Post-mixed fuel gas preheat scarfing



Jan. 25, 1966 w L AN 3,231,431

POST-MIXED FUEL GAS PREHEAT SCARFING Filed June 24, 1964 INVENTOR.

WILLIAM ALLMANG BY kw- ATTORNEY nite This application is acontinuation-in-part of my then pending but now abandoned applicationSerial No. 117,724, filed June 16, 1961, which is, in turn, acontinuation of my then pending but now abandoned application Serial No.843,651, filed October 1, 1959, which is, in turn, a continuation of mythen pending but now abandoned application Serial No. 682,103, filedSeptember 5, 1957.

This invention relates to post-mixed fuel gas preheat scarfing, and moreparticularly to method of thermochemical removal of metal from a surfacethereof with a wide continuous stream of cutting oxygen preheated by afuel gas selected from the group consisting of natural gas, propane,methane and coke oven gas.

In the use of natural gas for preheat flames such as in hand operatedoxyfuel blowpipes, the natural gas has been premixed with oxygen.Heretofore, it has been an unsolvable problem to employ post-mixednatural gas flames with continuous slot scarfing units.

Mainly, the problem is to have a post-mixed preheat flame adhere to theface of the flame ports. The precise reasons for this problem are notknown. Several reasons are put forth as explanations. To obtain the samepreheat effect with natural gas, it is necessary to use several timesthe amount of gas that would be required if acetylene were used. As aresult, natural gas must be used at higher pressures and velocities. Ahigh velocity flow may cause the natural gas preheat flame to blowoffthe preheat block.

Secondly, natural gas has a lower rate of flame propagation. That is,natural gas will not burn back fast enough to keep the flame on thetips.

It is therefore the main object of the present invention to provide ascarfing process having a continuous slot oxygen stream and post-mixednatural gas preheat flames.

According to the present invention the efliuent natural gas is confinedto a path substantially parallel to the cutting oxygen stream and thenatural gas is shielded to prevent mixture with atmospheric air. Forsome unknown reason, when the natural gas is so confined and shielded, astable, uniform post-mixed preheat flame is obtained. Without thisshielding, it is impossible to keep the flames on the tip. The probableexplanation is that the bafl le strips confine the gas and producebetter mixing with the cutting oxygen.

Also, the invention comprises an improvement on continuous slot scarfingunits which comprise securing a baffle strip to the upper and lowerpreheat blocks. The same results are obtainable using one-piece preheatblocks machined to the same contour.

In the drawings:

FIG. 1 is a side elevation of a scarfing head provided with post-mixednatural gas preheat according to the present invention;

FIG. 2 is a front elevation of the same normal to the oxygen slot; and

FIG. 3 is a view similar to FIG. 1 showing a modified construction.

As shown in the drawing, the oxidizing gas is projected in a widecontinuous stream S at an acute angle of impingement onto the reactionzone R, which extends transversely across the entire width of the workW. The stream is confined by an outer surface T and an inner surface B.

States Patent 0 The outer surface T extends smoothly and continuouslyforwardly along the stream S toward the reaction zone beyond the innersurface B for a distance greater than the thickness of the stream S.This extension of the outer surface T forms an overhanging lip L, thefront edge of which is close to the horizontal projection of the frontedge of the inner surface B.

An outer transverse row of jets of preheat fuel gas P is projectedinwardly at an acute angle against the outside of the stream S beyondthe front edge of the lip L, and an inner row of preheat fuel gas jets Fis projected outwardly at an acute angle against the inside of thestream S beyond the front edge of the inner surface B. The outer preheatjets are thus located nearer along the stream to the zone of reactionthan the inner preheat jets for a dis tance greater than the thicknessof the stream.

The confining of the upper surface of the stream of oxidizing gas beyondthe lower surface thereof and nearer to the reaction zone prevents thetendency of the gas to expand and escape, and also preventscontamination of the stream by outside air. In operation, the stream ofoxidizing gas tends to hug or cling to and follow the underside of theoverhanging lip L, and so be projected in a straight line continuingonto the reaction zone with a decreased amount of turbulence.

The location of the outer preheat jets nearer to the reaction zoneincreases the heat transfer to and temperature rise of the reactionzone, greatly facilitating starting, and increasing the efliciency ofthe reaction, because the hottest part of the preheat flame is broughtnearer to the reaction zone. Also, the outer preheat flames themselvestend to confine the oxidizing gas stream and shield it fromcontamination.

The location of the inner preheat jets facilitates heat transfer to thestream of oxidizing gas, which arrives at the reaction zone in a highlyheated condition.

According to the present invention natural gas is suppiled to thepreheat fuel passages P and F. A baffle strip 10 is secured to the frontface of the upper preheat block above the preheat fuel passage P, and asimilar baffle strip 12 is secured to the front face of the lowerpreheat block below the preheat fuel passages F. The thickness M ofthese strips are preferably one half inch as shown in FIGS. 1 and 3. Thelower surface of bafiie strip 10 attached to the upper preheat block andthe upper surface of baffle strip 12 attached to the lower preheat blockshould each be located as close to the preheat ports P and F as possibleAs shown in the drawings, the distance D from the lower surface ofbaflie strip 10 to the surface T of the upper preheat block isapproximately of an inch. Similarly, the distance D measured from theupper surface of the baflie strip 12 to the surface B of the lowerpreheat block is approximately of an inch. Consequently, the actualdistance from the surface of each baflie strip to each row of preheatports P and F is less than A; of an inch. Baflle strips 10 and 12 act toconfine both sides of the post mixed stream formed from the natural gasissuing from the upper and lower preheat ports P and F and the preheatflow of oxygen issuing as a wide continuous stream S. It is believedthat this confining action of the baflie strips upon both sides of theoxygen-fuel mixture prevents atmospheric air from aspirating thereintoat a point adjacent each row of preheat ports.

It has been found to be a critical requirement of this invention thatthe baffle strips 10 and 12 be contiguous with respect to each preheatblock as shown in the drawing. In FIG. 1, for example, it is importantto note that baflies 10 and 12 are in contact with the edge of the upperand lower preheat blocks, respectively. In FIG. 3, of course, the bafliestrips 10 and 12 are formed as an integral part of the upper and lowerpreheat blocks, respectively. The effect of having the baifie stripscontigous with respect to each preheat block is that it preventsatmospheric air from being aspirated through any spacing between thebaffle strips and the preheat blocks into the oxygen-fuel mixture at apoint close to the preheat ports P and F. The aspiration of even aminute quantity of air at this point will cause instability of thepost-mixed oxygen-natural gas flame. Even a spacing of a few thousandthsof an inch between the rear surface I and the edge of the preheat blockwill have a substantial effect on the stability of the post-mixedoxygen-natural gas flames issuing from the preheat ports P and F.

In the form shown in FIG. 1, the battle strip 12 is secured to the lowerpreheat block by bolts 15 countersunk into the strip, and all gapsfilled with silver solder. The surface is then machined to a 45 degreeangle as at 17. This triangular construction avoids forming a pocketbetween the strip 12 and the lower preheat block in which slag couldbuild up. Instead, this construction causes the slag to slide forwardand be blown away by the preheat gases.

As shown in FIG. 3, the bafiles are formed integral with the preheatblocks. The upper preheat block is extended forward and machined to forma surface 14 spaced outwardly from the oxygen slot S and extendingparallel thereto forwardly from the natural gas jets P. The lowerpreheat block is similarly machined to form a similar surface 16 toconfine the natural gas from the jets F.

While the invention has been described in connection with the use ofnatural gas as a fuel, it is equally applicable when the fuel gas ispropane, methane or coke oven gas.

What is claimed is:

1. In a process of thermochemically scarfing a metal body by discharginga sheet-like stream of oxidizing gas onto a reaction zone extendingacross the metal body and at an acute angle of impingement to the worksurface thereof, and wherein fuel gas is discharged from orifice meansand directed against at least one side of said stream of oxidizin gas,the improvement which comprises shielding the effluent fuel gas from itspoint of discharge to prevent aspiration of atmospheric air thereintoimmediately adjacent said point of discharge by a baflie surfaceextending forwardly from immediately adjacent the point of dischargetoward the reaction zone whereby a stable post-mixed fuel gas-oxidizinggas preheat fiame will be maintained.

2. In a process for thermochemically scarfing a metal body bydischarging a sheet-like stream of oxidizing gas onto a reaction zoneextending across the metal body and at an acute angle of impingement tothe work surface thereof, and wherein fuel gas is discharged fromorifice means and directed against each side of said stream of oxidizinggas, the improvement which comprises shielding the effluent fuel gasfrom its point of discharge against aspiration of atmospheric airthereinto by a surface extending forwardly from immediately adjacentsaid orifice means toward the reaction zone whereby stable postmixedfuel gas-oxidizing gas preheat flames will be maintained.

3. A process as claimed in claim 1 wherein oxygen comprises saidoxidizing gas and a member selected from the group consisting of naturalgas, propane, methane and coke oven gas comprises said fuel gas.

4. In a continuous slot scarfing unit wherein a central passage isprovided for discharging a sheet-like stream of oxygen for reaction witha metal surface to be scarfed and wherein orifice means are provided fordischarging fuel gas against at least one side of said stream of oxygen,the improvement which comprises means for shielding the efiluent fuelgas from its point of discharge from said orifice means to preventaspiration of atmospheric air thereinto adjacent said point ofdischarge, said means having a baffie surface extending forwardly fromimmediately adjacent said point of discharge toward the reaction zonewhereby a stable post-mixed oxygen-fuel gas preheat flame will bemaintained.

What is claimed is:

5. In a process for thermochemically scarfing metal bodies by confiningthe inside and outside of a supply of oxidizing gas to form a stream ofsubstantially uniform thickness, discharging said sheet-like stream ofoxidizing gas onto a reaction zone extending across a metal body and atan acute angle of impingement to the work surface of said metal body andcontinuing the confinement of the outside of said stream of oxidizinggas smoothly and continuously farther along the stream toward thereaction zone than the inside of said stream for a distance greater thanthe thickness of the stream, and discharging fuel gas from orifice meansdirected against both sides of said discharge oxidizing gas streambeyond the confinement thereof on its way to said reaction zone at anacute angle of impingement therewith, the improvement which comprisescontinuing the flow of said discharged fuel gas at the same acute anglebut in the same general direction as the oxidizing gas stream withoutinterruption into admixture with the oxidizing gas stream, and confiningthe outer sides of the commingled effluent fuel gas and oxidizing gasmixture beyond the confinement of said stream of oxidizing gas on itsway to said reaction zone by a surface substantially parallel to eachside of said oxidizing gas stream, and extending forwardly fromimmediately adjacent said orifice means smoothly and continuouslyfarther along the commingled stream toward the reaction zone to shieldthe flow of said efliuent and prevent aspiration of atmospheric airthereinto at a point immediately adjacent said orifice means, wherebypost-mixed fuel gasoxidizing gas preheat flames will be maintained.

6. A process as claimed in claim 5 wherein oxygen comprises saidoxidizing gas and a member selected from the group consisting of naturalgas, propane, methane and coke oven gas comprises said fuel gas.

7. In a process for thermochemically scarfing metal bodies bydischarging a sheet-like stream of oxidizing gas onto a reaction zoneextending across a metal body and impinging at an acute angle to thework surface of said metal body, confining said sheet-like stream ofoxidizing gas between surfaces respectively nearer to and farther fromsaid work surface, said farther surface extending smoothly andcontinuous forwardly and terminating in a front edge beyond the frontedge of said nearer surface in overhanging relation thereto for adistance measured along said stream and greater than the distancebetween said surfaces, to bring the front edge of said farther surfaceclose to the horizontal projection of the front edge of said nearersurface and discharging fuel gas from orifice means directed against atleast one side of said discharged oxidizing gas stream at an acute angleof impingement therewith, the improvement which comprises continuing theflow of said discharged fuel gas at the same angle but in the samegeneral direction as the oxidizing gas stream without interruption, andconfining the outer side of the commingled effluent fuel gas-oxidizinggas mixture beyond said farther surface in the direction of saidreaction zone by a surface substantially parallel to the outside of saidoxidizing gas stream, and extending contiguou'sly from said edge of saidfarther surface and immediately adjacent said orifice means smoothly andcontinuously farther along the commingled stream toward the reactionzone to shield the flow of said commingled stream to prevent aspirationof atmospheric air thereinto at a point immediately adjacent saidorifice means, whereby a post-mixed fuel gas-oxidizing preheat flamewill be maintained.

8. In a continuous slot scarfing unit wherein said slot is formedbetween an upper preheat block and a lower preheat block in spacedrelation to one another and wherein means are provided for dischargingan oxygen stream through said slot for reaction with a metal surface tobe scarfed, the improvement which comprises orifice means fordischarging a stream of preheat fuel gas from a point adjacent the edgeof each of said preheat blocks, and means comprising a 'batfie stripcontiguously extending from said edge of each of said preheat blocks ina direction substantially parallel to the axis of said slot andimmediately adjacent said orifice means.

6 References Cited by the Examiner UNITED STATES PATENTS 10/1936Rendleman 148--9.5 X 6/1954 Bucknam et a1. 266-23

1. IN A PROCESS OF THERMOCHEMICALLY SCARFING A METAL BODY BY DISCHARGING A SHEET-LIKE STREAM OF OXIDIZING GAS ONTO A REACTION ZONE EXTENDING ACROSS THE METAL BODY AND AT AN ACUTE OF IMPINGEMENT TO THE WORK SURFACE THEREOF, AND WHEREIN FUEL GAS IS DISCHARGED FROM ORIFICE MEANS AND DIRECTED AGAINST AT LEAST ONE SIDE OF SAID STREAM OF OXIDIZING GAS, THE IMPROVEMENT WHICH COMPRISES SHIELDING THE EFFLUENT FUEL GAS FROM ITS POINT OF DISCHARGE TO PREVENT ASPIRATION OF ATMOSPHERE AIR THEREINTO IMMEDIATELY ADJACENT SAID POINT OF DISCHARGE BY A BAFFLE SURFACE EXTENDING FORWARDLY FROM IMMEDIATELY ADJACENT THE POINT OF DISCHARGE TOWARD THE REACTION ZONE WHEREBY A STABLE POST-MIXED FUEL GAS-OXIDIZING GAS PREHEAT FLAME WILL BE MAINTAINED. 